1. Field of the Invention
This invention relates to safety devices, and more particularly to arrangements for protecting electrically fired ammunition or the like from premature or undesired ignition due to electrostatic charge or electromagnetic radiation.
2. Description of the Prior Art
It has long been known that the firing of ammunition by electrical ignition provides certain advantages over the percussion method. Electrical ignitors for ammunition provide shorter detonation times and are more reliable. The proportion of misfires is greatly reduced; in fact, misfiring is virtually eliminated, particularly where a combination electrical and percussion type primer is used which has the capability of igniting the primer by percussion if the electrical ignition system should malfunction. Because of these advantages, electrically fired ammunition is often preferred, particularly by the military, in those weapon systems which admit of adaptability to electrically fired ammunition. The Phalanx close-in weapon system of the U.S. Navy is one such installation. Examples of prior art disclosing electrically fired ammunition may be found in U.S. Pat. Nos. 690,268 of Gortz, 3,815,507 of Irish et al, and 3,844,216 of Jakobs et al, and in the German Pat. No. 2,245,308 and the French Pat. No. 2,231,945.
With the advent of electrically fired ammunition, there is the increased hazard of accidental firing due to the presence of sufficient ambient electrical energy to set off the ignitor. In some instances, the energy required for ignition may be as low as a few hundred ergs. Sufficient ambient energy to ignite electrically fired ammunition may be common in certain environments where systems using such ammunition are installed--e.g. radar-controlled guns--or from the build up of electrostatic charges in personnel or facilities which handle the ammunition. The recognition of this problem is also of long standing and examples in the prior art of various approaches for dealing with it may be found in the U.S. Pat. Nos. 1,959,479 of Kielczewski, 2,916,994 of O'Neill (shielding for electric blasting caps), 3,018,732 of Tognola, and 3,618,523 of Higuera.
In the Phalanx weapon system, for which the present invention was specifically developed, particular measures have been taken to guard against the accidental or inadvertent firing of the electrically ignited ammunition used in that system. The 20 mm ammunition which is employed is protected against ignition by electrostatic discharge and by electromagnetic radiation by virtue of a specially devised clip device, called the RADHAZ (for radiation hazard) clip to correct the problem. This clip is designed to keep the ignition electrode grounded when the ammunition is in storage. In preparation for use, the ammunition is transferred to a belt which transports the ammunition from the magazine drum to the actual weapon for firing. During this transfer step, special protection means are provided through the use of grounding fingers which ride along the ignitor electrodes of the individual rounds of ammunition. Despite these elaborate and specifically devised techniques, recent testing has revealed that the 20 mm round with the RADHAZ clip is vulnerable to radiation frequencies common to the Phalanx environment. In addition, during the same test program, the round was found to be vulnerable to ignition while in the flexible chute belt (without the RADHAZ clip) that feeds the rounds from the magazine drum to the gun breech.